Fuel injection pump for internalcombustion engines



Oct. 31, 1944. B. BOLLI ETAL 2,361,817

FUEL INJECTION PUMP FOR INTERNAL-COMBUSTION ENGINES 5 Sheeis-Sheet 2 Filed March 26, 1942 nmmumu B. BOLLI ET AL FUEL INJECTION PUMP FOR INTERNAL-COMBUSTION ENGINES Oct. 31 1944.

Filed March 26, 1942 5 Sheets-Sheet 3 & 2

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' B. BOLLI EIAL fld m w ojrh ll ll ll Oct. 31, 1944. BOLLl AL 2,361,817 FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES w Ma r/ 6 E a Fw Patented Oct. 31, 1944 FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Y Berfihard Bolli and Heinrich Bek, Arbon, Switseriand, assignors to Bocit Anonyme Adolph Saurer, Arbon, Switzerland E Application March 20, 1942, Serial No. 4.30.2.6: 7

In Germany June 10, 1940 I M '1 f Claims. (Cl. 1021-41).v 1

This invention relates to fuel injection pumps for internal combustion engines.

It has particular reference to injection pumpsof the short-delivery type, in which the time available for feeding fuel into the pump chamber is inversely proportional to the engine speed.

It is an object of this invention to provide a pump of the .kind aforesaid which is more effective than similar injection pumps hitherto devised and which is simpler in design and operation, while rendering superfluous the provision of a special no-load governor such as was required as a rule in connection with former injection pumps of this type.

In the pump accordingto thisinvention means are provided for narrowing the fuel admission port of the pump by substituting for it a second fuel admission port which is controlled by an angular movement of the piston for the purpose to vary, when changing over to idle-running at low speed, the quantity of fuel fed to and filling the working chamber of the pump per unit of time.

In the drawings afilxed to this specification and forming part thereof various embodiments of the invention are illustrated diagrammatically by way of example.

In the drawings Fig. l is a curve diagram illustrating the interdependency between the engine speed and the quantity of fuel injected.

Fig. 2 is a sectional elevation of the first embodiment.

Figs. 3a and 3b are similar views of part of a second embodiment in the no-load and full-load positions, respectively,

a fourth embodiment at no-load and at full-load respectively.

Referring to the drawings and first to Fig. l.

the quantity V of fuel delivered by the injection pump is plotted against the engine speed n. The

full-line curve A with index m shows how, with -unchanged position of the fuel regulator, the

quantity injected by a pump as hitherto used varies as a function of the speed. At the maximum speed nm the quantity of fuel Vm is injected, as shown at I. If the engine speed were raised further '1... the quantity injected would at first remain constant ill t the limitinl speed 1 (point I) At this speed the time avail able for filling is just sufll-oient for completely filling the pump chamber. If the engine speed rises further, the filling period is insumcient for a complete filling of the pump chamber, and the quantity of fuel injected drops in proportion to the equation wherein V: is the quantity injected at a speed 1;:

which is greater than the limiting speed n.

ther slowing down of the engine, owing to inv creasing leakage losses. At partial load, within the lower range of speeds, the delivery curve, for an invariable position of the quantity regulator,

is similar to the curve Am. One such partial-load delivery curve is shown at A. With the reduction of injected fuel during idling periods the delivery curve drops as shown at A1. in Fig. 1. At the no-load speed up. the quantity of fuel Vr.

so is injected. The corresponding point on the delivery curve A1. is marked 3. According to this delivery curve, with the quantity-regulator remaining stationary, at a speed higher than an the quantity of fuel injected rises, at a speed lower than an it drops. With such a'delivery characteristic it is impossible to maintain the no-load speed 1a.. The engine will either stop or will run at too high speed. Therefore, with iniection pumps of this type as hitherto used, the speed m. can be maintained only, if the quantityregulating members of the injection pump are adjusted by means of a centrifugal governor or a pneumatic or hydraulic regulator for the injection of a smaller quantity, when the speed rises, and a larger quantity, when it drops.

According to this invention, now, by closing the main admission port through which fuel is I supplied to the pump chamber and substituting for it another, relatively narrow, admission port,

the dropping of the delivery curve towards B,

that would otherwise occur with a large admission port, is shifted to a lower range of speeds,

and, by appropriately dimensioning the narrow admission port, this shift extends into the region of the no-load speed 111.. The delivery curve obtained with the narrow port is marked C in Fig.

1. Simultaneously with the changing over to the narrow admission port, the pump must be adiusted for delivery of a large quantity of fuel. In the neighbourhood of the no-load speed up, and with a fixed adjustment of the quantityregulator, the Pump will now work according to the delivery curve C, so that as the speed rises, the quantity of fuelinjected drops, while with dropping speed the quantity injected rises. Thus the engine automatically adjusts itself to the speed an, even if influences from without tend to drive it away from this speed. According to whether the quantity-regulator is adjusted for injection quantities corresponding to curve A or As or A, the quantity of fuel injected rises, be-

. low the level of the no-load speed 11L, following curve C, until this curve intersects the corresponding curve A. Am orAs, respectively.

. ti'ol and cam regulation.

- Referring to Fig. 2, I is the pump piston, l

the cam-shalt, I a plunger, 8 a return spring. The pump cylinder 2 is formed with two ports I and l which are controlled by the pump piston I. In the lower end position of the piston, the

port I which serves'as a reflux port, remainspiston 3 is formed with a cam edge II, a recess i3 and a reflux bore H. The piston is operative-L 1y connected with a toothed sleeve l5 meshing with a rack i6 which can be reciprocated transversely to the piston axis. Delivery begins as soon as piston 3 during its upward stroke has covered the main admission port 1. Delivery ends when the cam edge II begins to uncover the reflux port I in the cylinder 2.

In the operation of this pump, when the rack II is shifted towards the left, the quantity of fuel injected through the main admission port 1 into the working chamber of the pump drops gradually, since the cam edge ill on the piston uncovers the reflux port after a progressively shorter stroke of the piston. With the cam edge II on the piston is associated a cam face 9 which, when the rack ii is shifted towards the left, uncovers the reflux port 8 only after the piston has gone through a longer stroke. In this position, which is shown in Fig. 2, the quantity of fuel delivered by the pump rises again considerably. However the rack It on being shifted toward the left by the spring I I carries along a lever l8 fulcrumed at 18 which displaces the needle 20 toward the left against the action of a spring 2|. The conical end of this needle enters and closes the main admission port 1. It is formed with a narrow T-shaped bore 22 which communicates with the suction chamber of the pump. With the needle in the closing position shown in the drawings, fuel from the suction chamber can enter the pump chamber ll only through the narrow bore 22 which constitutes another admission port of greatly restricted cross-sectional area of passage. It is so dimen- In Figs. Zia-3d a second embodiment is illustrated. Here the pump piston 23, in order to provide for the closing of the main admission 2 port I, is formed with an extension 24 which, when the piston is rotated by means of the rack it (not shown) into no-load position and the cam face I closes the reflux port I, closes the main admission port I. The extension 24 is formed with a narrow calibrated bore 25, which here constitutes the second (narrow) admission port and allows the working chamber ll of the pump to be fllled only incompletely at no-load speed, so

that notwithstanding the large-delivery adiustment brought about by the cam face 9, the pump delivers only the quantity of fuel required for idle-running. Delivery takes place in accordance with curve C in Fig. 1, point 3 being particularly characteristic, and the pump keeps the engine self-regulating at no-load speed as desired. When the piston is turned still further to the left in Figure 3a a groove 28 provided in the control surface of the piston is aligned with the main admission port I and keeps the working chamber II of the pump in communication with the suction chamber [2. The pump then no longer delivers fuel, and the engine comes to .a standstill. For starting the pump piston is rotated back into the position shown in Figure 3a. At the low speed at which the starter turns the motor, the charging period is suiflcient to completely flil the working chamber ll of the pump with fuel through the narrow admission port 25 and the pump now delivers the large quantity of fuel determined by For instance a rotary valve the cam surface I. With an appropriately formed surface 9 this quantity may be greater than the quantity of fuel delivered when the en ine runs under full load. The pump then operates in the region of point I of the diagram of Fig. 1.

In the position of the pump piston 23 shown v in Fig. 3b the pump is adjusted for injecting the full-load quantity of fuel. The main admission port I is uncovered, so that even at maximum engine speed the working chamber H of the pump pump cylinder 21, while the pump piston 20 is sioned that at no-load speed the pump chamber 76 formed at its upper end with a step 30, which keeps the reflux port 8 covered even in the lowest position of the piston, and which upon adjustment to slow idling (Fig. 4a) closes the main admission port I, so that in this position of the pump piston the working .chamber ll of the pump can be filled only through the narrow admission port 28. The cross section of this port is so dimensioned, that at no-load speed the working chamber H is only partially filled with fuel, whereby notwithstanding the long delivery stroke adjusted by the cam face 8, only the quantity of fuel Vi. needed for idling is delivered, the pump operating according to the characteristic C in F18. 1. In this position of the parts the pump at starting speed delivers the maximum quantity V- (Figure 1) determined by the cam face 0. Upon further rotation of the pump piston to the right beyond the position shown in Figure 4a, the longitudinal groove 28 takes up a position in iront of the reflux port 8, whereby delivery by the pump is interrupted, and the engine stops.

In this embodiment the groove 2| may be so dimensioned as to constitute the sole communication between the working chamber II and the space it adjoining the cam race 0. In that case the connecting conduit ll (Figs. 2, 3a and Bb) can be dispensed with. I

In Figs. 5a and 5b, a development of the control surface of the pump piston is shown, in which the cylinder ports are also indicated. Fig. 5a

shows the relative positions of the cam face and the cylinder ports during the idling and starting periods. Fig. 5b shows their relative positions during full-load operation. The cam face is de signed for the lowermost position of the pump piston.

engine, the working chamber H of the pump is,

not only filled but is also, at the end of injection, relieved only when covered by the cam edge [0.

In this pump the suction chamber i2 is not sep-,v

arated from the refiux chamber I2, as is the case in Figs. 2, 3 and 4. The small filling aperture 33,

for idling, is here arranged diametrically opposite the large aperture 1. The piston 34 is again formed at the upper end with a step or shoulder 30. by which the large filling aperture 1 is covered in the no-load position shown in Fig. 6a. The

' mode of operation of this arrangement will be In the no-load and starting positions the main admission port 1 is covered by the cam face.

in the direction of the arrow, delivery, if the working chamber of the pump is entirely filled with fuel, begins when the narrow admission port II is covered by the cam face. Delivery is interupted when the uncovering oi the reflux part I by the lower edge 3201 the cam face 9 begins. All this takes place at starting speed. The quantity of fuel delivered is determined by the piston stroke ha marked in Fig. 5a. At idling speed, however, the working chamber of the pump has not been completely filled. The shortage of fuel that occurred owing to the charging period being too short, corresponds to a piston stroke ho, so that delivery does not begin until the narrow admission port is located, in relation to the control face, in the lower position marked in Fig. 5a. Delivery then continues only during the piston stroke hl. The area of the piston multiplied by the stroke ha determines the quantity of fuel delivered at starting speed. The same area multiplied by the stroke '11 determines the quantity of fuel delivered at no-load speed.

An angular movement of the pump piston in Fig. 5, corresponding to a displacement of the developed control surface towards the right, leads to the full-load position shown in Fig. 5b. A slight rotation of the piston uncovers the main admission port 1, but the reflux port I still remains covered in the lowermost position of the piston. Owing to the large cross-sectional area of passage of the main admission port the working chamber of the pump is still completely filled, even at the highest engine speed. Delivery begins as soon as port 1 is covered by the control surface. It ends as soon as the reflux port 8 begins to be uncovered by the cam edge Ill. The delivery of the pump is accordingly determined by the stroke hm, shown in Fig. 5b, multipled by the area of the piston.

In Figs. (id-6d a further form of construction of the invention is shown, Figure 6a representing the position for idling and for starting and Figure 6b the full-load position of the pump piston. In the embodiments illustrated in Figures 2, 3

obvious from Figs. 6a and 6b after the above description. 1

The idea of the invention can be applied, on the general lines indicated, not only to a pump with piston-valve control and cam edge regulation but also to any otherkind of short-delivery pumps.

The cross section of the filling aperture that comes into action when running at idling speed. may be so designed as to be variable in size from the outside, for instance in a known manner by means of a conical needle engaging in this filling aperture and adjustable from the outside while the engine is running. It thereby becomes possible to adjust the no-load' speed of the engine to any desired value.

Instead of the no-load filling apertures 25 and 2t bored directly in the piston or in the cylinder as shown in Figs. 3a, 3b, and 4a, 4b, nozzles may be inserted, which may be exchangeable. The no-load speed of the engine can then be adiusted to the desired value by suitably selecting and exchanging these nozzles.

We wish it to be understood that we do not desire to be limited to the exact details above described, for obvious modifications will occur to a person skilled in the art.

We claim: I 1. In a fuel injection pump for internal combustion engines in combination, a pump cylinder and a piston formed with a control surface and arranged for cooperation with said cylinder in metering fuel into the working chamber of the pump, means for reciprocating said piston, means for imparting to it an angular movement about its axis, a main fuel admission port in the cylinder wall and a. second relatively narrow admission port under control by the angular movement of saidpiston for varying the quantity of fuel admitted into and filling the working chamber per unit of time.

2. The combination of claim 1, in which a throttling member arranged ior-coaction with the main admission port is formed with a bore forming the second admission port.

3. The combination of claim 1, in which one of the two cooperating parts is formed with the second admission port.

4. The combination of claim 1, in which an extension of the piston is formed with the second admision port.

5. The combination of claim 1, in which the second admission port is also formed in the cylinder wall and an extension of the piston is arranged to control both admission ports.

BERNHARD BOLLI. HEINRICH BEK. 

